Transmission fluid pump speed control systems and methods

ABSTRACT

A transmission fluid pump control system of a vehicle includes a target speed module and a speed control module. The target speed module determines a target speed of an electric transmission fluid pump based on a target output flowrate of the electric transmission fluid pump, a predetermined maximum allowable amount of leakage of transmission fluid pumps, and an efficiency of the electric transmission fluid pump. The speed control module applies power to the electric transmission fluid pump based on the target speed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/828,230, filed on May 29, 2013. The disclosure of the above application is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to vehicle transmissions and more particularly to speed control systems and methods for transmission fluid pumps.

BACKGROUND

The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

An engine generates torque and outputs torque to a transmission. An automatic transmission of a vehicle may include a plurality of fluid controlled friction elements, such as clutches. A control module may engage and disengage the friction elements to establish different gear ratios (also called speed ratios) within the transmission.

The transmission includes a transmission fluid pump. The transmission fluid pump provides transmission fluid for applying the clutches of the transmissions, lubricating transmission components, and cooling transmission components. Some transmission fluid pumps are mechanically driven, such as by the engine. Other transmission fluid pumps are electrically driven.

SUMMARY

A transmission fluid pump control system of a vehicle includes a target speed module and a speed control module. The target speed module determines a target speed of an electric transmission fluid pump based on a target output flowrate of the electric transmission fluid pump, a predetermined maximum allowable amount of leakage of transmission fluid pumps, and an efficiency of the electric transmission fluid pump. The speed control module applies power to the electric transmission fluid pump based on the target speed.

In further features, the target speed module determines the target speed of the electric transmission fluid pump further based on a displacement of the electric transmission fluid pump.

In still further features, the target speed module sets the target speed equal to a sum divided by the displacement and sets the sum based on the target output flowrate plus a product of the predetermined maximum allowable amount of leakage and the efficiency.

In yet further features, the target speed module sets the target speed equal to a sum divided by the displacement and sets the sum based on the target output flowrate plus the predetermined maximum allowable amount of leakage plus the efficiency.

In further features, an efficiency module determines the efficiency of the electric transmission fluid pump based on a speed determined for the electric transmission fluid pump and a predetermined speed for transmission fluid pumps having the predetermined maximum allowable amount of leakage.

In still further features, the efficiency module sets the efficiency of the electric transmission fluid pump equal to the speed determined for the electric transmission fluid pump divided by the predetermined speed.

In yet further features, a speed determination module determines the speed for the electric transmission fluid pump based on a pressure of transmission fluid measured using a transmission fluid sensor.

In further features, the speed determination module sets the speed for the electric transmission fluid pump equal to a present speed when a decrease in the pressure is greater than a predetermined pressure.

In still further features, the target speed module determines the predetermined maximum allowable amount of leakage based on a temperature of transmission fluid and a pressure of the transmission fluid.

In yet further features, a target flowrate module determines the target output flowrate of the electric transmission fluid pump based on a target output pressure of the electric transmission fluid pump.

A transmission fluid pump control method for a vehicle includes: determining a target speed of an electric transmission fluid pump based on a target output flowrate of the electric transmission fluid pump, a predetermined maximum allowable amount of leakage of transmission fluid pumps, and an efficiency of the electric transmission fluid pump; and applying power to the electric transmission fluid pump based on the target speed.

In further features, the transmission fluid pump control method further includes determining the target speed of the electric transmission fluid pump further based on a displacement of the electric transmission fluid pump.

In still further features, the transmission fluid pump control method further includes: setting the target speed equal to a sum divided by the displacement; and setting the sum based on the target output flowrate plus a product of the predetermined maximum allowable amount of leakage and the efficiency.

In yet further features, the transmission fluid pump control method further includes: setting the target speed equal to a sum divided by the displacement; and setting the sum based on the target output flowrate plus the predetermined maximum allowable amount of leakage plus the efficiency.

In further features, the transmission fluid pump control method further includes determining the efficiency of the electric transmission fluid pump based on a speed determined for the electric transmission fluid pump and a predetermined speed for transmission fluid pumps having the predetermined maximum allowable amount of leakage.

In still further features, the transmission fluid pump control method further includes setting the efficiency of the electric transmission fluid pump equal to the speed determined for the electric transmission fluid pump divided by the predetermined speed.

In yet further features, the transmission fluid pump control method further includes determining the speed for the electric transmission fluid pump based on a pressure of transmission fluid measured using a transmission fluid sensor.

In further features, the transmission fluid pump control method further includes setting the speed for the electric transmission fluid pump equal to a present speed when a decrease in the pressure is greater than a predetermined pressure.

In still further features, the transmission fluid pump control method further includes determining the predetermined maximum allowable amount of leakage based on a temperature of transmission fluid and a pressure of the transmission fluid.

In yet further features, the transmission fluid pump control method further includes determining the target output flowrate of the electric transmission fluid pump based on a target output pressure of the electric transmission fluid pump.

Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of an example vehicle system according to the present disclosure;

FIG. 2 is a functional block diagram of an example transmission system according to the present disclosure;

FIG. 3 is a functional block diagram of an example pump control system according to the present disclosure;

FIG. 4 is an example graph of transmission fluid pump speed and transmission fluid pressure as functions of time during a transmission fluid pump test;

FIG. 5 is a flowchart depicting an example method of testing a transmission fluid pump to determine an efficiency of the transmission fluid pump according to the present disclosure; and

FIG. 6 is a flowchart depicting an example method of controlling a transmission fluid pump according to the present disclosure.

In the drawings, reference numbers may be reused to identify similar and/or identical elements.

DETAILED DESCRIPTION

An engine generates drive torque for a vehicle. A transmission transfers torque to one or more wheels of the vehicle. A transmission fluid pump pumps transmission fluid from a transmission fluid source (e.g., a sump) to various components of the transmission, such as clutches. The transmission fluid pump is an electric pump. A control module controls a speed of the transmission fluid pump based on a target flowrate.

All transmission fluid pumps leak, such as between rotating components and inner walls. A vehicle manufacturer may require that all transmission fluid pumps leak (internally) less than or equal to a predetermined maximum allowable amount. The control module may control the speed of the transmission fluid pump based on the predetermined maximum allowable amount to ensure that the transmission fluid pump achieves the target flowrate if the transmission fluid pump's leakage is equal to the predetermined maximum allowable amount.

However, if the transmission fluid pump's leakage is less than the predetermined maximum allowable amount, the transmission fluid pump may be controlled to a faster speed than is necessary. The control module of the present disclosure therefore determines an efficiency of the transmission fluid pump relative to transmission fluid pumps with leakage equal to the predetermined maximum allowable amount. The control module controls the speed of the transmission fluid pump further based on the efficiency of the transmission fluid pump. Controlling the speed of the transmission fluid pump based on the efficiency may enable the transmission fluid pump to be operated at lower speeds and therefore consume less energy.

Referring now to FIG. 1, a functional block diagram of an example vehicle system is presented. An internal combustion engine 12 drives a transmission 14 via a torque converter 16. The engine 12 may include, for example, a spark-ignition engine, a compression-ignition engine, or another suitable type of engine. A vehicle may also include one or more electric motors and/or motor generator unit (MGUs), such as MGU 18.

The engine 12 outputs torque to the torque converter 16 via an engine output shaft 20, such as a crankshaft. The torque converter 16 supplies torque to the transmission 14 via a transmission input shaft 22. The electric motor(s) and/or MGU(s) may also output torque to the transmission input shaft 22 to supplement or replace engine torque output. A MGU may convert mechanical energy into electrical energy under some circumstances, for example, to recharge one or more batteries and/or to supply power for electronic components of the vehicle.

The transmission 14 includes one or more gearsets (not shown) for transferring between the transmission input shaft 22 and a transmission output shaft 24. A gear ratio may refer to the ratio between the rotational speed of the transmission input shaft 22 and the rotational speed of the transmission output shaft 24. The transmission output shaft 24 drives a driveline 26, and the driveline 26 transfers torque to wheels (not shown) of the vehicle. A range selector 28 enables a user to select a mode of operation of the transmission 14. The mode may include, for example, a park mode, a reverse mode, a neutral mode, or one or more forward drive modes.

An engine control module (ECM) 60 controls operation of the engine 12. The ECM 60 or another control module (not shown) may control operation of one or more electric motors and/or MGUs in various implementations. A transmission control module (TCM) 70 controls operation of the transmission 14. While the TCM 70 is shown as being implemented within the transmission 14, the TCM 70 may be implemented externally to the transmission 14 in various implementations. The ECM 60 and the TCM 70 may share data via a connection 72.

Referring now to FIG. 2, a functional block diagram of an example implementation of a transmission system is presented. The transmission 14 includes a plurality of friction coupling elements, such as first, second, third, fourth, and fifth clutches 104, 106, 108, 110, and 112, respectively. The transmission 14 may include a greater or fewer number of clutches and/or friction coupling elements.

The friction coupling elements control which one of the gear sets is engaged within the transmission 14 at a given time. Different gear ratios may be established when different combinations of one or more of the friction coupling elements and gear sets are engaged.

Transmission fluid 120 is directed to and from the friction coupling elements to control engagement and disengagement of the friction coupling elements. An electric transmission fluid pump 116 draws the transmission fluid from a sump 124 or another suitable transmission fluid source. The transmission fluid pump 116 pressurizes the transmission fluid and provides pressurized transmission fluid to a valve body 132. The transmission fluid pump 116 may also provide pressurized transmission fluid to the torque converter 16 and/or one or more other components.

The transmission fluid pump 116 may also output transmission fluid for lubrication of one or more transmission components and for cooling of one or more transmission components, such as one or more electric motors and/or MGUs. The transmission 14 may include a transmission fluid cooler (not shown) that transfers heat from transmission fluid flowing through the transmission fluid cooler to a cooling medium, such as air or coolant.

Some types of transmission fluid pumps are driven mechanically, such as by the engine 12. The transmission fluid pump 116, however, is an electric transmission fluid pump. A pump control module 135 (see also FIG. 3) applies electrical power from one or more batteries, such as battery 134, to the transmission fluid pump 116 to drive the transmission fluid pump 116. The transmission fluid pump 116 outputs transmission fluid based on the electrical power applied to the transmission fluid pump 116. Control of the transmission fluid pump 116 is discussed further below in conjunction with FIG. 3.

The valve body 132 includes one or more control solenoids, such as clutch control solenoid 138, that control the flow of the transmission fluid from the valve body 132 to ones of the friction coupling elements and vice versa. The transmission fluid flows between the valve body 132 and ones of the friction coupling elements via passages, such as passages formed in a housing 136 of the transmission 14. For example only, the clutch control solenoid 138 may control the flow of the transmission fluid 120 between the valve body 132 and the first clutch 104 via passage 139. One or more clutch control solenoids and passages may be provided for each of the friction coupling elements.

One or more line pressure regulator solenoids, such as line pressure regulator solenoid 140, control the flow of the transmission fluid from the valve body 132 (at a relatively higher pressure) back to the sump 124 (at a relatively lower pressure). By controlling the flow of the transmission fluid back to the sump 124, the line pressure regulator solenoids also control the pressure of the transmission fluid provided to the control solenoids and the friction coupling elements. For example only, the line pressure regulator solenoid 140 may control the pressure of the transmission fluid 120 provided to the clutch control solenoid 138 and the first clutch 104. One or more line pressure regulator solenoids may be provided for each of the clutch control solenoids.

The transmission 14 may include one or more pressure sensors. For example only, a line pressure sensor 160 may measure a pressure of the transmission fluid provided to the clutch control solenoid 138. The TCM 70 may control the line pressure regulator solenoid 140 to adjust the pressure of the transmission fluid provided to the clutch control solenoid 138 toward a target line pressure. The pressure of the transmission fluid provided to the clutch control solenoid 138 will be referred to as a line pressure. A line pressure sensor may be provided for each of the clutch control solenoids. The transmission 14 includes one or more other sensors, such as a transmission fluid temperature sensor 162.

Referring now to FIG. 3, a functional block diagram of an example pump control system is presented. The pump control module 135 may be implemented independently, within the TCM 70, or within another suitable module. A target flowrate module 204 determines a target flowrate 208 of transmission fluid output by the transmission fluid pump 116. The target flowrate module 204 may determine the target flowrate 208, for example, based on a target pressure 212, one or more lubrication requests 216, one or more cooling requests 220, and/or one or more other parameters.

The target pressure 212 may correspond to a target pressure of transmission fluid output from the transmission fluid pump 116. A lubrication request may be generated to request that the transmission fluid pump 116 output transmission fluid for lubrication of one or more components. A cooling request may be generated to request that the transmission fluid pump 116 output transmission fluid for cooling of one or more components.

A target speed module 224 determines a target speed 228 of the transmission fluid pump 116 based on the target flowrate 208. However, all transmission fluid pumps, including the transmission fluid pump 116, leak (internally) to some extent. For example, transmission fluid may leak between rotating components of the transmission fluid pump 116 and internal walls of the transmission fluid pump 116 due to clearances between the rotating components and the internal walls. It should be noted, however, that leakage of the transmission fluid pump 116 remains contained within the transmission.

The amount of leakage may vary from transmission fluid pump to transmission fluid pump, but a vehicle manufacturer may require that all transmission fluid pumps leak less than or equal to a predetermined maximum allowable amount of leakage. For example only, a vehicle manufacturer may require the amount of leakage be less than approximately 4 Liters per minute (LPM), approximately 5 LPM, or another suitable maximum allowable amount of leakage.

The predetermined maximum allowable amount of leakage may vary by line pressure and/or temperature of the transmission fluid. A mapping of values of the predetermined maximum allowable amount indexed by line pressure and/or transmission fluid temperature may be stored in memory, such as memory 236.

The target speed module 224 determines a predetermined maximum leakage 232 and determines the target speed 228 further based on the predetermined maximum leakage 232. The target speed module 224 may determine the predetermined maximum leakage 232 from the mapping based on line pressure and/or transmission fluid temperature, or the predetermined maximum leakage 232 may be a constant value.

Determining the target speed 228 based on the predetermined maximum leakage 232 ensures that the transmission fluid pump 116 achieves the target flowrate 208, even if the actual amount of leakage of the transmission fluid pump 116 is equal to the predetermined maximum leakage 232. However, if the actual amount of leakage of the transmission fluid pump 116 is less than the predetermined maximum leakage 232, the transmission fluid pump 116 may be operated at a speed that is greater than necessary to achieve the target flowrate 208.

The target speed module 224 therefore determines the target speed 228 further based on an efficiency 240 of the transmission fluid pump 116. The target speed module 224 may determine the target speed 228 using one of a function and a mapping that relates the target flowrate 208, the predetermined maximum leakage 232, and the efficiency 240 of the transmission fluid pump 116 to the target speed 228. For example, the target speed module 224 may determine the target speed 228 using the equation:

${{{Target}\mspace{14mu} {Speed}} = \frac{{{Target}\mspace{14mu} {Flow}} + \left( {{Max}*{Efficiency}} \right)}{Displacement}},$

where Target Speed is the target speed 228, Target Flow is the target flowrate 208, Max is the predetermined maximum leakage 232, Efficiency is the efficiency 240, the efficiency 240 is a gain value between 0.0 (corresponding to no leakage) and 1.0 (indicating leakage equal to the predetermined maximum leakage 232), and Displacement is the displacement of the transmission fluid pump 116. The displacement of the transmission fluid pump 116 is a predetermined value and may be stored in the memory 236. In various implementations, the target speed module 224 may alternatively determine the target speed 228 using the equation:

${{{Target}\mspace{14mu} {Speed}} = \frac{{{Target}\mspace{14mu} {Flow}} + {Max} + {Efficiency}}{Displacement}},$

where Target Speed is the target speed 228, Target Flow is the target flowrate 208, Max is the predetermined maximum leakage 232, Efficiency is the efficiency 240, the efficiency 240 is an offset value between 0.0 (indicating leakage equal to the predetermined maximum leakage 232) and a negative value of the predetermined maximum leakage (indicating no leakage), and Displacement is the displacement of the transmission fluid pump 116.

The target speed module 224 may determine the target speed 228 further based on one or more other parameters, such as one or more flowrates to provide cooling and a valve body leakage (e.g., rate). For example, the target speed module 224 may sum the flowrates to provide cooling and the valve body leakage with the numerators of the equations above before dividing by the displacement. The valve body leakage may refer to a leakage rate of the valve body 132. The target speed module 224 may determine the valve body leakage and the flowrates to provide cooling, for example, based on transmission fluid temperature and pressure of the transmission fluid output by the transmission fluid pump 116.

A speed control module 242 applies power to the transmission fluid pump 116 based on the target speed 228. For example, the speed control module 242 may determine a pulse width modulation (PWM) duty cycle to be applied to the transmission fluid pump 116 based on the target speed 228 and apply power to the transmission fluid pump 116 at that duty cycle.

An efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116. The efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116 based on predetermined data for transmission fluid pumps with leakage equal to the predetermined maximum leakage 232 and data obtained for the transmission fluid pump 116 before the vehicle is made available to the public.

More specifically, the efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116 based on a pump speed where a transmission fluid pressure decrease occurs for transmission fluid pumps having the predetermined maximum leakage 232. This pump speed is a predetermined speed 248 and may be stored in the memory 236.

The efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116 further based on a speed of the transmission fluid pump 116 where the transmission fluid pressure decrease occurred using the transmission fluid pump 116. The transmission fluid pressure is monitored during a test performed before the vehicle is made available to the public to identify the pump speed for the transmission fluid pump 116. This pump speed will be referred to as a test pump speed 252.

In implementations where the efficiency 240 is a gain value between 0.0 and 1.0, the efficiency module 244 may set the efficiency 240 equal to the test pump speed 252 divided by the predetermined speed 248. In other implementations, the efficiency module 244 may determine the efficiency 240 using one of a function and a mapping that relate the test pump speed 252 and the predetermined speed 248 to the efficiency 240. In various implementations, the efficiency module 244 may selectively adjust the predetermined speed 248 based on one or more parameters, such as pressure and/or temperature of the transmission fluid.

A speed determination module 256 determines the test pump speed 252 during the test before the vehicle is made available to the public. A mode signal 258 may indicate that the test is occurring. The test includes decreasing a pump speed 260 and monitoring a line pressure 264. The line pressure 264 may be measured using the line pressure sensor 160 or measured using a sensor at a test facility where the vehicle is tested before the vehicle is made available to the public. While the test will be described in terms of using the line pressure 264, another suitable transmission fluid pressure may be monitored, such as a transmission cooler outlet pressure. The pump speed 260 may be measured using a speed sensor or determined based on one or more parameters.

When a decrease in the line pressure 264 occurs, the speed determination module 256 reads the pump speed 260 and stores the read pump speed as the test pump speed 252. The decrease may occur, for example, when the line pressure 264 decreases from an initial value by at least a predetermined amount, such as approximately 50 kiloPascals (kPa) or another suitable amount.

Referring now to FIG. 4, an example graph of pump speed 304 and line pressure 308 as functions of time during the test is presented. As stated above, the speed control module 242 decreases the pump speed 304 during the test. For example, the speed control module 242 may decrease the pump speed 304 at a predetermined rate as shown in FIG. 4.

The pump speed 304 where a decrease in the line pressure 308 by at least the predetermined amount occurs for transmission fluid pumps with leakage equal to the predetermined maximum leakage 232 is referred to as the predetermined speed 248. The predetermined speed 248 is indicated in FIG. 4 by 312.

The pump speed 304 where the decrease in the line pressure 308 by at least the predetermined amount occurs using the transmission fluid pump 116 is referred to as the test pump speed 252. The speed determination module 256 monitors the line pressure and sets the test pump speed 252 based on or equal to the pump speed 260 when the line pressure decreases by at least the predetermined amount. The test pump speed 252 is illustrated in FIG. 4 by 316.

The relationship between the predetermined speed 248 and the test pump speed 252 corresponds to how much the transmission fluid pump 116 leaks relative to the predetermined maximum leakage 232. The efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116 based on the predetermined speed 248 and the test pump speed 252, and the target speed module 224 determines the target speed 228 based on the efficiency 240 as described above.

Referring now to FIG. 5, a flowchart depicting an example method of determining the test pump speed 252 is presented. Control may begin with 404 where the speed determination module 256 determines an initial value of the line pressure 264. The initial value of the line pressure 264 may be determined before, after, or when the decrease in the pump speed 260 begins. In various implementations, an average or another suitable statistical parameter determined based on one or more samples of the line pressure 264 may be used as the initial value.

At 408, the speed determination module 256 reads the line pressure 264 and determines whether the line pressure 264 has decreased from the initial value by at least the predetermined amount. If true, the speed determination module 256 stores the pump speed 260 as the test pump speed 252 at 412, and control may end. If false, control may remain at 408. For example only, the predetermined amount may be approximately 50 kPa or another suitable pressure. As stated above, the relationship between the predetermined speed 248 and the test pump speed 252 corresponds to how much the transmission fluid pump 116 leaks relative to the predetermined maximum leakage 232.

Referring now to FIG. 6, a flowchart depicting an example method of determining the target speed 228 and controlling the transmission fluid pump 116 is presented. Control may begin with 504 where the target flowrate module 204 determines the target flowrate 208. At 508, the efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116. The efficiency module 244 determines the efficiency 240 of the transmission fluid pump 116 based on the predetermined speed 248 and the test pump speed 252. For example, the efficiency module 244 may set the efficiency 240 equal to the test pump speed 252 divided by the predetermined speed 248.

At 512, the target speed module 224 determines the target speed 228. The target speed module 224 determines the target speed 228 based on the target flowrate 208, the predetermined maximum leakage 232, and the efficiency 240. The target speed module 224 may determine the target speed 228 using one of a function and a mapping that relates the target flowrate 208, the predetermined maximum leakage 232, and the efficiency 240 of the transmission fluid pump 116 to the target speed 228. For example, the target speed module 224 may determine the target speed 228 using the equation:

${{{Target}\mspace{14mu} {Speed}} = \frac{{{Target}\mspace{14mu} {Flow}} + \left( {{Max}*{Efficiency}} \right)}{Displacement}},$

where Target Speed is the target speed 228, Target Flow is the target flowrate 208, Max is the predetermined maximum leakage 232, Efficiency is the efficiency 240, the efficiency 240 is a gain value between 0.0 (corresponding to no leakage) and 1.0 (indicating leakage equal to the predetermined maximum leakage 232), and Displacement is the displacement of the transmission fluid pump 116. The displacement of the transmission fluid pump 116 is a predetermined value and may be stored in the memory 236. In various implementations, the target speed module 224 may alternatively determine the target speed 228 using the equation:

${{{Target}\mspace{14mu} {Speed}} = \frac{{{Target}\mspace{14mu} {Flow}} + {Max} + {Efficiency}}{Displacement}},$

where Target Speed is the target speed 228, Target Flow is the target flowrate 208, Max is the predetermined maximum leakage 232, Efficiency is the efficiency 240, the efficiency 240 is an offset value between 0.0 (indicating leakage equal to the predetermined maximum leakage 232) and a negative value of the predetermined maximum leakage (indicating no leakage), and Displacement is the displacement of the transmission fluid pump 116. The target speed module 224 may determine the target speed 228 further based on one or more other parameters, such as the flowrate(s) to provide cooling and/or the valve body leakage. At 516, the speed control module 242 controls the application of power to the transmission fluid pump 116 based on the target speed 228.

The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.

In this application, including the definitions below, the term module may be replaced with the term circuit. The term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory may be a subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer readable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage.

The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory tangible computer readable medium. The computer programs may also include and/or rely on stored data. 

What is claimed is:
 1. A transmission fluid pump control system of a vehicle, comprising: a target speed module that determines a target speed of an electric transmission fluid pump based on a target output flowrate of the electric transmission fluid pump, a predetermined maximum allowable amount of leakage of transmission fluid pumps, and an efficiency of the electric transmission fluid pump; and a speed control module that applies power to the electric transmission fluid pump based on the target speed.
 2. The transmission fluid pump control system of claim 1 wherein the target speed module determines the target speed of the electric transmission fluid pump further based on a displacement of the electric transmission fluid pump.
 3. The transmission fluid pump control system of claim 2 wherein the target speed module sets the target speed equal to a sum divided by the displacement and sets the sum based on the target output flowrate plus a product of the predetermined maximum allowable amount of leakage and the efficiency.
 4. The transmission fluid pump control system of claim 2 wherein the target speed module sets the target speed equal to a sum divided by the displacement and sets the sum based on the target output flowrate plus the predetermined maximum allowable amount of leakage plus the efficiency.
 5. The transmission fluid pump control system of claim 1 further comprising an efficiency module that determines the efficiency of the electric transmission fluid pump based on a speed determined for the electric transmission fluid pump and a predetermined speed for transmission fluid pumps having the predetermined maximum allowable amount of leakage.
 6. The transmission fluid pump control system of claim 5 wherein the efficiency module sets the efficiency of the electric transmission fluid pump equal to the speed determined for the electric transmission fluid pump divided by the predetermined speed.
 7. The transmission fluid pump control system of claim 5 further comprising a speed determination module that determines the speed for the electric transmission fluid pump based on a pressure of transmission fluid measured using a transmission fluid sensor.
 8. The transmission fluid pump control system of claim 7 wherein the speed determination module sets the speed for the electric transmission fluid pump equal to a present speed when a decrease in the pressure is greater than a predetermined pressure.
 9. The transmission fluid pump control system of claim 1 wherein the target speed module determines the predetermined maximum allowable amount of leakage based on a temperature of transmission fluid and a pressure of the transmission fluid.
 10. The transmission fluid pump control system of claim 1 further comprising a target flowrate module that determines the target output flowrate of the electric transmission fluid pump based on a target output pressure of the electric transmission fluid pump.
 11. A transmission fluid pump control method for a vehicle, comprising: determining a target speed of an electric transmission fluid pump based on a target output flowrate of the electric transmission fluid pump, a predetermined maximum allowable amount of leakage of transmission fluid pumps, and an efficiency of the electric transmission fluid pump; and applying power to the electric transmission fluid pump based on the target speed.
 12. The transmission fluid pump control method of claim 11 further comprising determining the target speed of the electric transmission fluid pump further based on a displacement of the electric transmission fluid pump.
 13. The transmission fluid pump control method of claim 12 further comprising: setting the target speed equal to a sum divided by the displacement; and setting the sum based on the target output flowrate plus a product of the predetermined maximum allowable amount of leakage and the efficiency.
 14. The transmission fluid pump control method of claim 12 further comprising: setting the target speed equal to a sum divided by the displacement; and setting the sum based on the target output flowrate plus the predetermined maximum allowable amount of leakage plus the efficiency.
 15. The transmission fluid pump control method of claim 11 further comprising determining the efficiency of the electric transmission fluid pump based on a speed determined for the electric transmission fluid pump and a predetermined speed for transmission fluid pumps having the predetermined maximum allowable amount of leakage.
 16. The transmission fluid pump control method of claim 15 further comprising setting the efficiency of the electric transmission fluid pump equal to the speed determined for the electric transmission fluid pump divided by the predetermined speed.
 17. The transmission fluid pump control method of claim 15 further comprising determining the speed for the electric transmission fluid pump based on a pressure of transmission fluid measured using a transmission fluid sensor.
 18. The transmission fluid pump control method of claim 17 further comprising setting the speed for the electric transmission fluid pump equal to a present speed when a decrease in the pressure is greater than a predetermined pressure.
 19. The transmission fluid pump control method of claim 11 further comprising determining the predetermined maximum allowable amount of leakage based on a temperature of transmission fluid and a pressure of the transmission fluid.
 20. The transmission fluid pump control method of claim 11 further comprising determining the target output flowrate of the electric transmission fluid pump based on a target output pressure of the electric transmission fluid pump. 